Asexual
Reproduction
Species are maintained in existence through the life spans
process of reproduction. Asexual reproduction
produces genetically identical offspring from a single parent
cell. The process of mitosis is associated with
asexual reproduction and the growth and repair of cells in
sexually reproducing organisms.

Reproduction and development are necessary for the
continuation of any species. Asexual reproduction is a
method of reproduction with all the genetic information coming
from one parent.

Some
Methods of Asexual Reproduction

1. binary fission
-- involves an equal division of both the organism
cytoplasm and nucleus to form two identical organisms

-- the diagram of mold
spores being formed at the right is an example of this

Asexual
reproduction is sometimes called cloning. Cloning is
the production of identical genetic copies. All forms of
asexual reproduction are variations of the cell division
process of mitosis. Mitosis is associated with asexual
reproduction, as well as growth and repair in sexually
reproducing organisms.

Mitosis
Mitosis is the method used for cell division and
reproduction in cells not involved in sexual reproduction. This process starts with one replication (copying of
the chromosome material) and one division of the chromosome
material. This results in the chromosome numbers in the
two cells produced being the same as in the parent cell. This process is represented in the graphic which follows.

An
Overview of the Process of Mitosis

The Cell CycleThe cell cycle is the lifespan of a cell. It is
divided into three parts: Interphase, Mitosis, and
Cytokinesis. Interphase is divided into three parts. G1
- or the first growth phase, is the stage in a cells life when
normal cell functioning is occurring. A cell will remain in
this stage unless it receives a signal to reproduce. Cells can
receive signals from neighboring cells during development of a
multi-cellular organism, or it may receive a signal for repair
of neighboring cells or a cell may receive a signal to divide
if the cell becomes too large for intracellular transport to
occur effectively. When a cell receives the signal to divide,
it moves into the second stage of interphase called
synthesis. Synthesis is the longest part of the cell cycle
because this is the stage when a cells DNA replicates. DNA
replication involves separating the double helix,
complimentary nucleotides finding their match (Adenine joins
with Thymine, Cytosine joins with Guanine) and two identical
strands of DNA forming. Once this is accomplished, and
proteins have confirmed its success, a cell moves into the
third phase of interphase called G2, or the second growth
phase. Here, organelles replicate and the cell grows in
anticipation of dividing into two smaller cells.

If everything goes according to
plan, a cell is ready to move into the mitotic stage of the
cell cycle. Mitosis is the division of the nucleus
stage. It is a choreographed mechanism to efficiently and
accurately divide the two identical copies of DNA into the
newly forming cells and it is done the same way in every
living cell. The four parts of this cycle are prophase,
metaphase, anaphase and telophase (PMAT). In prophase,
the DNA which is in long, stringy chromatin form
condenses and coils up into chromosomes. The identical
pieces of DNA are joined together with a centromere. During
this phase, the nuclear membrane in eukaryotes begins to
disintegrate. In metaphase, the paired chromatids
line up (chromosomes) single file down the equator of the
cell. In anaphase, the sister chromatids separate and
identical chromatids each move to opposite poles. Telophase
is when the chromosomes begin to uncoil again back into
chromatin and new nuclear membranes begin to form in
eukaryotes.

The final stage of the cell cycle
begins in telophase when the cells cytoplasm begins to divide.
In animal cells, the cell membrane pinches in during this
stage called cytokinesis. In plant cells, a cell plate
forms between the newly forming nuclei as the cell wall can't
pinch in. This continues until two new cells are formed with
identical DNA.

2 Key Results of Mitosis

1. The same chromosome number is
retained from generation to generation.
2. Each daughter cell receives an exact copy of the
chromosomes of the parent cell. (clones)

Asexual
HeredityEvery organism requires a set
of coded instructions for specifying its traits. For offspring
to resemble their parents, there must be a reliable way to
transfer information from one generation to the next.
Heredity is the passage of these instructions from one
generation to another. The DNA molecule provides the
mechanism for transferring these instructions.

In asexually
reproducing organisms, all the genes come from a single
parent. As asexually produced offspring are produced by the
cell division process of mitosis, all offspring are
normally genetically identical to the parent.